As you stand there, you can’t help but look at the trillions of litres of water right in front of you. But it’s salt water, and you know you shouldn’t drink it. You’re not sure why, but deep down you know it’s off limits.

Surely a few drops won’t hurt, maybe just half a cup. You’ll die if you don’t drink something soon, so what’s the worst that can happen?

In these situations, it isn’t enough to just know something’s off limits. When push comes to shove, and when everything’s on the line, you can rationalise your way around anything; even drinking sea water. So the question remains: why can’t we drink sea (salt) water?

Firstly, Why Do We Need Water?

Our bodies are mostly water, between 70 and 80%, depending on whom you talk to. The water in our bodies supports many functions, including waste removal and temperature regulation. Since water is consumed and expelled by these functions, we need to constantly replenish our water reserves to survive.

How Do Our Bodies Regulate Temperature?

In most situations, your body regulates temperature using radiation and convection. In short, this just means your body sends heat to the surface (skin), so cooler air around you can absorb the heat. But this is only effective if the external air is cooler than your body.

Lauren and Adheip riding camels in the Egyptian desert heat

When the outside air becomes hotter than your body, you perspire to regulate temperature. This is not about dampening and cooling the skin; quite the opposite actually. Your body dilates the blood vessels near the skin (sending more hot blood through them) and excretes sweat to effect evaporation. The process of evaporation requires energy, and that energy comes from the heat in your blood and skin. By consuming heat to effect evaporation, your body essentially cools itself, particularly its core (brain and vital organs).

How Do Our Bodies Absorb Water?

You may remember the process of osmosis from science class at school. Osmosis occurs across a semi-permeable barrier (our cell membranes). That barrier allows water molecules to pass in certain directions, depending on the concentration of water solutions on each side (imagine different concentrations of salt water).

Our cells aim for this isotonic (equal) state, where the salt concentration is the same on both sides.

In normal circumstances, the saltiness of water in your cells is the same as the saltiness outside your cells. This is called an isotonic state. But when your cells consume water, the solution becomes more concentrated, and the natural process of osmosis allows water from outside your cells to pass into your cells to achieve equilibrium (this is called osmoregulation). That’s how we absorb water as it’s needed; it’s a natural process.

Why Can’t We Drink Too Much Pure Water?

Your cells are isotonic to about 0.9% saline solution. If the salinity of the solution outside the cells decreases, your cells absorb more water to get back to an isotonic state.

When we drink too much fresh water, excessive water passes into our cells to try to regulate the concentration (which can become futile). This causes cells to swell and sometimes burst.

When marathon runners and other endurance athletes drink too much fresh water, the solution outside their cells drops rapidly in salinity, so osmosis allows water to pass into the cells as a part of osmoregulation. If they absorb too much water, the cells will swell and burst, which can lead to a quick death. This is why runners drink sports drinks that contain sodium and potassium, to help maintain an isotonic state (and it’s why they’re called isotonic sports drinks).

Why Can’t We Drink Too Much Salt (Sea) Water?

The opposite happens when drinking sea (salt) water. The salinity outside your cells increases rapidly, so osmoregulation effects a movement of water from in your cells, to outside your cells, to achieve an isotonic state. So even though you may be dehydrated, your cells will actually release, rather than absorb, the water around them.

But why would your dehydrated body expel water when death is imminent? Well, this isn’t a conscious decision by your body. It’s simply molecular physics and osmosis at work. And in osmosis, water passes from low saline concentrations to high saline concentrations, end of story.

When we drink salt water, water leaves our cells (dehydrating us further) in order to regulate (dilute) the concentration of the salt water we just drank (again, futile).

So, you should absolutely not drink sea or salt water when dehydrated. It’s not just an issue of not absorbing the water, but an issue of osmosis accelerating the release of water and dehydration.

I said in the introduction, “You’ll die if you don’t drink something soon, so what’s the worst that can happen?” Well, what’s worse than dying? Dying much sooner, potentially before help arrives.

Hey Bessie, thanks for dropping by and many thanks for the kind words. I didn’t see the salt water master cleanse on your list of 29 things to do by 29. Just make sure it doesn’t coincide with extreme dehydration in the desert. May run into a few problems :)

Really interesting article. Earlier this year I spent three months at sea and had to use a desalinator to convert salt water in to drinking water. There were a couple of days when we didn’t have enough power to run it though and after reading your article very pleased I resisted the urge to drink straight from the sea…

Thanks for dropping by Luke; I just checked out your site… what an adventure that was?! If you ever consider running your own expeditions with clients, let us know because we’re slowly moving into that area. We’d love Globetrooper to become a hub for finding participants for unique adventures.

Ripley Davenport listed his Gobi 2011 expedition on Globetrooper and I believe he got a handful of clients as a result (including Lauren and me).

Todd.
Thanks for the details in the article. As an engineer, I research things by nature. And now as a runner, I’ve been looking into this more. I remember the issue of not drinking sea water, and that it will dehydrate you faster. My question is, “At what concentration does the drink go from good-for-you to bad-for-you?” I just finished training for and running a marathon which featured Gatorade Pro; which almost doubles the amount of sodium (200mg/8 oz). I remembered the issue from my biology class and your article, and was wondering, where is the Gatorade Pro in relation to sea water? Could I be drawing water out of my body by because of the salinity of the drink?
Thanks,
Pete.

Hey Pete, The sodium concentration of human blood is 0.9%. So Gatorade Pro concentration seems quite a bit under that, say 200mg / 224g. Sea water is over 3% concentration. Interesting though, because some of those drinks taste really salty. The last time I drank Gatorade on a competition run it made me feel sick and I think I lost about 5 minutes. Just this week we had an electrolyte solution from the pharmacy that didn’t contain sugar and it was much better in terms palatability. Don’t get me wrong, I like Gatorade in normal circumstances, but in competition the taste is too sickly sweet for me. I much prefer water. The run I’m taking about is only 14km and I’m drinking less than 1 litre, so probably no risk of brain swelling or whatever happens to marathon runners after too much water. I wonder why they don’t make Gatorade at 0.9% salinity then? Probably trying to avoid what you mentioned because sodium is consumed through other sources.

Very interesting! I’m a stewardess and a part of our training course and every day exams is survival in a desert and sea, too. We were always told NEVER drink sea water but never knew all the details why. Now I know, thanks :)

Great information here! I’m like everyone else. Always knew we weren’t supposed to do it, but never knew why. I also had no idea it would SPEED UP the dehydration process, just always thought it wouldn’t help it. Great post!

Bio-teacher here. i was looking for info specific to the effects of salinity (as in sea water) on the ‘sodium pump’ in the loop of Henle`in the kidney tubules, how it affects the hormone Aldosterone -doesn’t this increase salt uptake by the blood, which by osmosis, increases water re-absorption… from the CELLS I suppose, and the collecting ducts would still have too much salt so would NOT let water be re-absorbed by the kidney medulla or by the blood… so urine would still be produced. Another question: How does the chlorine in tap water affect the sodium pump in the Loop of Henle`? -and how does this affect osmoregulation?

Felicia again, -seeing your pic of the camels; Did you know that camels have much longer Loops of Henle` in their kidney nephrons than other mammals like us? -An adaptation to survival in the desert; they re-absorb more water in the kidneys and produce less urine which is highly concentrated as a result. they also store fat, not water, in their humps -fat metabolism produces water…

“But when your cells consume water, the solution becomes more concentrated, and the natural process of osmosis allows water from outside your cells to pass into your cells to achieve equilibrium (this is called osmoregulation).”

I’m not sure what ‘the solution’ is referring to (inside or outside the cell). I suspect the problem is with your choice of the words ‘consume water’, which perhaps should be ‘expel water’, or ‘are in need of water’.

I don’t believe it. Listen – sea water is water and salt. When I am dehidrayted I don’t have much water left in my body. So when I drink sea water, I console SOME water. Therefore I will have more water in my body than before. I will no longer be dehydrated.

Drinking very limited amounts of seawater, in desperate situations, can keep you alive for a little longer. Your body can process a bit of salt water, but certainly not enough to quench your thirst.

So if you’re on a raft in the middle of the ocean, and you have no other options (rain, condensation, fish, etc…), and you have the discipline to keep your seawater intake very low, it might extend your life by a day or two, which could be enough to be rescued.

You’d have to be pretty desperate, though. This stuff is definitely not good for you, and it will make you crazy if you drink more than small amounts.

Water is considered highly saline if it contains anywhere from 10,000-35,000 ppm of dissolved salts. Water is considered fresh if it contains less than 1,000 ppm of salt. In some regions of the United States, slightly saline water is used for tasks like crop irrigation. In regions where an abundant supply of clean, fresh water is difficult to come by, desalinization technologies convert seawater to drinkable fresh water. This is still a very expensive process, although costs are starting to drop, and methods, such as reverse osmosis, are improving. Today, the towns of Avalon and Santa Barbara in California, and Tampa Bay in Florida, are working on desalinization projects.

But that still doesn’t answer your question. So, we typed “why can’t humans drink salt water” directly into the search box. The U.S. government came through again with an answer from the Department of Energy’s Ask a Scientist web site. Prof Bill’s response is brief and to the point:

Humans can’t drink salt water because the kidneys can only make urine that is less salty than salt water. Therefore, to get rid of all the excess salt taken in by drinking salt water, you have to urinate more water than you drank, so you die of dehydration.

As is so often the case, this answer raises some new questions. How much salt is too much? Salt, like water, is a key ingredient of life on earth. The right amount of sodium chloride (common table salt) is essential for human health. In fact, our blood is 0.9% salt and our body weight is about 1/400 salt. Living cells depend on sodium chloride to maintain the chemical balances required for complex processes and reactions that take place at the microscopic level.

Insufficient salt intake can lead to fatigue, illness, and death, although it is more common nowadays to hear about health problems associated with too much salt. According to the Salt Institute’s encyclopedic site about salt, the National Academy of Sciences’ recommended daily dose is 500 mg/day — though most Americans consume closer to 3,500 mg/day. (A teaspoon of salt equals about 2,000mg.)

Optimal salt intake varies — it depends on a person’s genetic makeup, where they live, how active they are, and other lifestyle factors. However, nobody, except for a saltwater fish, is designed to drink saltwater.

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But if this is soooooo planned, I still get the impression the Fed and their banksters are fully in control of the coming currency crisis. Then they MUST have a plan for the gold and silver in the aftermath of whatever financial apocalypse we may see

Well, they’ve already had two prominent public figures murdered by Islam in the Netherlands;Pim FortuynandTheo Van Gogh of the Vincent Van Gogh familyFortuyn was not murdered by a Muslim, but was instead murdered by a Islam-sympathizing Leftist.The net effect of these murders is that many in the Netherlands have woken up, but the government still largely ignores the problem.Happy 4th of July, Damien. I hope you are going to get to do something enjoyable.

So for survival purposes. If I am stranded at sea and I have a gallon of water. Would it make sense to double my water supply by mixing 50/50 seawater/pure water? Reducing the salinity to 1.5%? IF it’s too much, would it make sense to have a higher ratio of pure water first so as to slowly increase the salinity inside your cells?

thanks for the article.
very interesting and familiar to me;
did a lot of research myself and travelled 3 years on camelback through deserts.
but someone tried and succeeded? (drinking salt water floating on the ocean)http://en.wikipedia.org/wiki/Alain_Bombard

Sea water can be used to cool your body, in the same way as sweat does. By emersion or splashing your body in sea water the cooling effect will help to reduce sweating, and thus help to reserve your water. May not be enough to keep you alive for long though.

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Under normal conditions, our bodies should be in an __________________ state, where the concentrations of water in our cells equals that of outside of our cells. n:

In his book, Sea Salt’s Hidden Powers, Dr. Jacques de Langre talks about the healing power of sea salt. “It can help in correcting excessive acidity; restoring good digestion’ relieving allergies and skin diseases; and preventing many forms of cancer. Natural salt provides a steady boost in cellular energy and give the body a heightened resistance to infections and bacterial diseases”.

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Hey! I can understand how salt water is bad for you if you drink it instead of regular water. But I don’t know if you’ve heard of salt water flushes, it’s something that has been used for hundreds of years in Asian cultures I think it is. And now salt water flushes is an important step in sowmthing called master cleanse. But since the salt water flush is so old I don’t see how this can be dangerous it’s an effective way of cleaning out your colon and digestive system. I would be very happy if you could give me your thoughts and opinions on that :) greats article!

I know this is a strange question, but when I vacation to the ocean and spend a lot of time lounging in the water, I never get thirsty. I will literally not drink any water for hours yet continue to urinate. Is my body somehow absorbing the water it needs from salt water?

Excellent read, I just passed this onto a friend who was doing some research on that. And he just bought me lunch because I found it for him smile Therefore let me rephrase that: Thanks for lunch! “Too much sanity may be madness. And maddest of all, to see life as it is and not as it should be” by Miguel de Cervantes.

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Okay so you can’t drink it. The next question I have regarding the above scenario is, you’re at the desserts edge by the sea. Would it still be better to take a dip at least? Cooling off would stop you from sweating it out. Also, if one can absorb water through the skin, you’d think it would strain out the salt.

Hi, since water is small liquid and is important, and it is more pure than other drink, there is small solid that is important which is salt. Salt and water can mixed together. So, salt is more important than other solid, small kind because it have higher charge?? So, there are cell, cell that have external environment outside, and cell that have internal environment. Since cell affect the whole body as we are as a whole one big cell, but it is various of cell. So, it is important for water to be inside of cell, and salt to be outside cell. Water is energy and carrier of energy, so it absorbs anti-energy that is salt, so salt will cause decrease in water. So, since logically there are two process in cell, outside to inside cell, so there are two mass process that cause the process in body. Water and salt. So, if drink water alone, without food, you will died because water will shrink the cell, since there is not enough salt in body. There are two things that is positive and negative. So, water is positive, and salt is negative, so include other liquid that is not water, but other stuff is balance, high balance or low balance that lead to either suck water out of cell or release or cell absorbs water from what you drink. That does include food, so the whole point in down to body is two process to be absorb in (enter cell) or suck out (exit cell). Are all cell is same size of whole body, so same salt and water in whole body? But density of cell which group into organs have higher or lower density of ratio of water and salt. Water is pure as enter cell more easily; salt is pure as exit cell more easily. So, there is ratio of suck out inside food and liquid; there is ratio of absorb in inside liquid and food. So, all food have salt in it; if no salt, then water in it. So, salt and water are essential, well, highest level essential. If there is no water at all, what happen to food and liquid? When I say water, I mean all water, macro and micro. If there is no salt at all, what happen to food? That is micro and macro salt? Well, would it be right to say that water is primary essential, and salt is secondary essential. So, if there is no salt at all, the food will be good for our body?? There is flavor, yes, but where do flavor come from? Salt? What about milk, there is micro water in milk. So, in non-water, there is water in it. In non-salt as percent of sodium in chart, there is salt in it. But micro-salt. Water is call liquid alone; salt is a mineral that can mixed well with water, but there are other mineral that don’t mixed well with water, but same important as salt. It come down to balance in cell.

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